Hi there. What do you mean by spikey leaves? Are they long, narrow and pointed or are they actually sharp to the touch? The shape looks a like Artemisia vulgaris to me, but without a better closeup pic, the green leaves or the flower, it's very difficult to tell. http://en.wikipedia.org/wiki/Mugwort
Is the stalk round, ridged and red tinged? That would be another indication that it is A. vulgaris. There are many other Artemisias as well and all are medicinal.
Good luck with the id!
"Forgive me if I never visit. I am from the fields, you know, and while quite at home with dandelion, make a sorry figure for the drawing room" ~Emily Dickinson
It is kind of hard to tell from the photo because this was obviously taken way after the plant was still in its prime, but it looks a bit like Sericea lespedeza to me. The various conservation departments across the U.S. got farmers and ranchers to introduce the stuff as a wildlife food back in the 30s or 40s (quail, pheasants, wild fowl and livestock love it) but, like kudzu, it turned out to be a very bad idea. Now, all the conservation people are busy telling people how to eradicate this invasive weed.
It would be helpful to know where you live and some of the conditions in which you found the plant. Dry or wet soil? Shade or sun? Is it in an old field or garden or out in an undisturbed area? (From the stuff in the background, I'm guessing a barnyard.) Were there a lot of them or just one? Do you see any seeds? If so, what do they look like? How tall/wide is the plant? Any odor upon crushing the leaves? And so on...
I agree with another poster that artemisia is a possibility as well, though I would suggest A. caudata rather than vulgaris.
It does help to know what geographical region it would be in. Here in Western Montana, if I find things that I don't know what they are, I found a good website for identifying nearly everything, you may try the same with googling your state name and the word weeds. We also have a local branch of the state's agriculture department to go with the plant specimen for identification in the worst case scenario. And you may have to wait until it grows back and is green and full-grown again. I will stay posted on this thread to see what you discover!